A full envelope submarine depth control system incorporating switched h∞ controllers

In this paper we discuss the application of H_∞ Optimisation techniques to the design of a control system for a submarine. The dynamics of a submarine change significantly with speed and to cover the speed envelope from 3 to 18 knots we have developed a strategy based on switching of H_∞ controllers. The necessary compensation to achieve bumpless tansfer during switching is also the basis of a controller conditioning strategy for maintaining performance in the presence of actuators. In addition we discuss a nonlinear feedforward strategy (incorporating a trajectory generator) which provides improved peformance. Nonlinear simulation results demonstrate the effectiveness of these approaches. These implementation issues are crucial if multivariable controllers are to find widespread application in industrial (nonlinear) applications.